Thrust regulator comprising a mounting enclosure

ABSTRACT

A regulator is housed in the expulsion channel of an aerosol container inside which there is a product that is to be dispensed, this product being subject to an expulsion pressure originating from a compressed gas, the said regulator comprising a flexible disk (6) and a rigid disk (7), the latter presenting a protrusion (8) with grooves (9), and further comprising a sealing disk (12) with a central bore (13), and further comprising a nozzle (16). With the flexible disk (6), the grooves (9) in the rigid disk (7) form ducts for the expulsion of the product, and are oriented so as to form tangents to the circumference of the axial duct (10) of the rigid disk (7). This arrangement of the component parts creates turbulence effects in the flow of expelled product, and these effects are utilized to regulate the flow rate at which the product is expelled.

The present invention relates to a thrust regulator which comprises amounting enclosure, this thrust regulator being intended to maintain theflow rates of liquid or cream-like products at values that remain atleast approximately constant during the expulsion of these products fromaerosol containers by means of compressed gas, in accordance with theprecharacterizing clause of claim 1.

It is known that compressed gases, such as, for example, air ornitrogen, exhibit a pressure drop as soon as there is an increase in thevolume of the container in which they are stored, such as occurs in thecase of an aerosol container from which a product is being expelled. Theflow rate of this product decreases in proportion to this fall inpressure. At the same time, when the product is atomized by means of anozzle, there is an increase in the size of the droplets which areexpelled, due to insufficient expulsion pressure.

U.S. Pat. No. 4,487,334 and International Patent Application No.PCT/CH83/00122, published under the number WO 84/01930, describe thrustregulators which modify the flow cross-section of a duct, with the aidof a piston which co-operates with a spring, doing so under theinfluence of the pressure which expels the product from the aerosolcontainer, in such a way that when the pressure is high, the flowcross-section is small, and increases in proportion to the fall inexpulsion pressure.

These regulators, manufactured in molded plastic, nevertheless demandvery high precision if they are to function well, in the region of ±0.01mm in the case of a piston diameter of less than 1 mm, such precisionbeing very expensive. In fact, certain solvents, in particular methylenechloride, give rise to swelling of the plastic which is used, and thiscauses the piston to jam inside the expulsion duct and, in consequence,causes the system to become blocked.

The object of the present invention is to eliminate these problems, andto propose a thrust regulator of the type defined in claim 1, annexedhereto.

In the description which follows, preferred, non-limiting embodiments ofthe invention are described on the basis of the drawing, in which

FIG. 1 a cross-sectional view of a press-to-actuate head, comprising afirst embodiment of a regulator according to the invention,

FIG. 2 shows an exploded view, in perspective, of a second embodiment ofa regulator,

FIG. 3 shows a perspective view of a first variant of a regulating diskwhich a regulator contains,

FIG. 4 shows an exploded view, in perspective, of a third embodiment ofa regulator,

FIG. 5 shows a cross-sectional view of a second variant of a regulatingdisk which a regulator contains,

FIG. 6 shows, a plan view of the regulating disk shown in FIG. 5,

FIG. 7 shows a cross-sectional view of a fourth embodiment of aregulator, before it is used,

FIG. 8 shows a cross-sectional view of the regulator shown in FIG. 7,during use,

FIG. 9 shows perspective views of different variants of the regulatingdisk,

FIG. 10 shows an exploded view, in perspective, of a fifth embodiment ofa regulator,

FIG. 11 shows a cross-sectional view of a sixth embodiment of theregulator,

FIG. 12 shows a plan view of another variant of the regulating disk,placed on an accelerating disk,

FIG. 13 shows a perspective view of the arrangement shown in FIG. 12,

FIG. 14 shows a cross-sectional view of a portion of the regulating diskshown in FIG. 12, greatly enlarged, at rest, and

FIG. 15 shows a cross-sectional view of the portion of the regulatingdisk shown in FIG. 14, during use.

FIGS. 1 and 2 show a regulator which is housed in a press-to-actuatehead 1, associated with an aerosol valve which is not represented. Avertical duct 2, communicating with the valve, opens into a chamber, 4,which exhibits a widened region 5. The chamber 4 is closed-off by aflexible disk 6, which is preferably made of stainless steel, but whichcan also be composed of a plastic. The flexible disk 6 is housed in thewidened region 5, where it is kept in place by means of a rigid disk 7.This disk 7 presents a convex protrusion, 8, which is provided with aplurality of grooves 9, arranged in a manner such that they formtangents to the circumference of an axial duct 10. The grooves 9 presentsteps, 11, which are intended to create turbulence effects in theproduct which is passing through the regulator, under pressure. The disk7 bears against a sealing disk 12, which is also preferably made ofstainless steel, and which is provided with a bore 13. A nozzle 16,presenting a protruding portion 15 and grooves 14, bears against thesealing disk 12, in a manner such that the grooves 14 act as ducts.

The PCT Application which has already been cited describes theappearance of turbulence effects when the flow of a pressurized liquidis deflected through a right angle in the presence of a rod, in thiscase a piston, located in the duct upstream, these turbulence effectsconstituting a flow-retarding force, and being capable of developing sofar as to stop the outflow. This retarding force is directlyproportional to the pressure under which the liquid is being expelled:the higher the pressure, the greater the retarding force.

The same Patent Application describes the automatic control of thisretarding force, so as to regulate the thrust with which a product isexpelled from an aerosol container. However, in this known application,the turbulence effects, and the retarding force which they create,depend also on the presence of a piston that is housed in a chamber 17of the nozzle 16. If this piston is absent, the retarding force due tothe turbulence effects is weaker.

In order to eliminate the necessity for a high-precision plastic moldingfor the purpose of obtaining the required quality of regulation, thepresent invention does not involve a piston. So as to compensate for thelack of turbulence-created retarding force, due to the lack of a piston,the convex protrusion 8 is provided with grooves 9, which become ductsby virtue of the fact that the flexible disk 6 bears hard against them.Because these ducts form tangents to the periphery of the axial duct 10in the rigid disk 7, turbulence effects appear, creating a retardingforce, adding to the retarding force which is created by the nozzle 16,but which is weakened by the lack of a piston, in such a way that theregulator, as described, is endowed with a two-stage "turbulator". Sincethe disk 6 is flexible, it allows itself to be deformed by the pressureunder which the product is expelled, in such a way that, given theconvexity of the protrusion 8, the ducts present minimum flow crosssections under a high expulsion pressure, these sections enlarging inproportion to any fall in the expulsion pressure, following an extremelysmall displacement of the flexible disk 6 in the upstream direction. Forthis reason, flow regulation is brought about just as effectively by theenlargement of the flow cross-sections of the ducts 9, following a fallin expulsion pressure, allowing the flexible disk 6 to relax, as byvariations in the retarding force due to turbulence effects, followingvariations in the expulsion pressure.

The appearance of turbulence effects depends on the viscosity of theproduct which is to be expelled in order to be atomized by means of thenozzle 16. It has been noticed that, once the viscosity exceeds 8centipoises, the retarding force due to the turbulence effects starts todecrease, if the regulator operates as described, just as does thequality of regulation. In order to make good this quality shortfall, theflexible disk 6 can be replaced by a regulating disk 18, as illustratedin FIG. 3. In a first variant, this regulating disk 18 exhibits notches,19 and 20, from which the leaf springs 21 and 22 result. When thepressure under which the product is expelled is high, the leaf springs21 and 22 are depressed, and close-off at least two of the ducts 9. Themore the expulsion pressure falls, the more the leaf springs 21 and 22relax, in a manner such that the closed-off ducts 9 are opened in likeproportion. When the regulator operates in this way, the quality ofregulation is provided partly by the turbulence effects, butpredominantly by the variations in the flow cross-sections of the ducts9.

FIG. 4 presents another embodiment of a regulator, which is intended fordispensing viscous products, such as creams, oils, mustards, etc. Giventhat products of this kind, exhibiting high viscosities, do not generateturbulence effects, their flow rates have to be regulated solely byvarying the flow cross-sections under the influence of the fall in theexpulsion pressure provided by the compressed gases which are utilized.

Within a cylindrical seating 23 in a press-to-actuate head 24, arehoused, upstream, a flexible disk 25, a first flexible regulating disk26, presenting a leaf spring, 27, which can temporarily close a cut-out28, a rigid disk 29, exhibiting a chamber 30 and an axial duct 31, theprotrusion 8 not being visible, a flexible disk 32, a second flexibleregulating disk 33, presenting a leaf spring, 34, which can temporarilyclose a cut-out 35, and a flexible disk 36, exhibiting a bore 37, thewhole assembly being held in place by means of a dispensing device 38.

The design details of the two flexible regulating disks, 26 and 33, areillustrated in FIGS. 5 and 6, which show them in cross-section and planview respectively. The leaf springs 27 and 34, being sensed to bringabout the temporary closing-off of the cut-outs 28 and 35, must beadjusted perfectly, and in order to prevent them from jamming in thecut-outs 28 and 35 they are provided, at their bases, with raisedportions, 39, which give them enough spring force to prevent them fromjamming in the said cut-outs. In order to ensure that a minimum passagepersists after closure of the cut-outs 28 and 35, each of the leafsprings 27 and 34 presents a small beak 40 at its free end, these beaks40 shortening the active spring length by an amount which is a functionof the angle 41.

The embodiment of the regulator as shown in FIG. 4 operates in a mannerwhich is illustrated by FIGS. 7 and 8, where the regulator is housedinside a cylinder 43, inside which a chamber 44 and an axial duct 46 areprovided, the chamber 44 exhibiting a widened region 45. When theregulator is at rest, namely if no product is flowing out via theaerosol-container valve, which is not represented, the duct 46 isclosed-off by the flexible disk 25, which is kept in the illustratedposition by means of the leaf spring 27 belonging to the first flexibleregulating disk 26, which, for its part, is kept in place by the rigiddisk 29, this latter disk being provided with the protrusion 8 and theaxial duct 31.

The rigid disk 29 exhibits the chamber 30, in which the flexible disk 32is housed, held in place by the leaf spring 34 of the second flexibleregulating disk 33, which bears against the flexible disk 36. Thecomplete assembly is held in place by the dispensing device 38. When thevalve, which is not represented, is opened, the product 47, expelled bythe pressure acting inside the aerosol container, presses the flexibledisk 25 in the downstream direction, thus opening the axial duct 46while displacing the leaf spring 27 in the downstream direction,partially closing the cut-out 28 and leaving open only a flowcross-section which corresponds to the expulsion pressure. At the momentof maximum expulsion pressure, this passage will be minimal, by virtueof the small beak 40. Thus, at any moment while the valve is open, theproduct 47 can flow out via the axial duct 31, and can act on theflexible disk 32, which in its turn displaces the leaf spring 34 of thesecond flexible regulating disk 32 in the downstream direction, placingit over the mouth of the bore 37, this movement reducing thecross-section available for flow through this bore, to an extent whichdepends on the expulsion pressure but, by virtue of the small beak 40,leaving a minimum passage at any time while the valve is open, via whichpassage the product 47 can flow out via the dispensing device 38,through a duct 48. As the pressure expelling the product 47 falls, theleaf springs 27 and 34 press the flexible disks 25 and 32proportionately more and more in the upstream direction, thus openingthe cut-outs 28 and 35 more and more, in such a way that the productflow rate remains at least approximately constant.

FIG. 9 shows advantageous variants of the flexible regulating disks 26and 33, presenting different numbers of variously-shaped leaf springs 27and 34, for taking account of a desired flow rate, and for takingaccount of the viscosity of the product 47 which is to be dispensed. Theforce exerted by the leaf springs 27 and 34 can be varied by varying thewidth over which they are attached to the flexible regulating disks 26and 33.

FIG. 10 shows another embodiment of a regulator, such as isadvantageously utilized in the press-to-actuate head according to theinvention. This regulator is intended to refine the regulation,especially for utilizing the regulator as a means of atomizing ahairspray in a manner enabling it to be applied to the hair with a coneof atomization exhibiting an angle which is as constant as possible.Given that the appearance of retardation-creating turbulence effectsdepends on the product viscosity, and that the viscosity of thehairspray may be variable, depending on the quality of "hold" required,the regulation due to turbulence effects has to be supplemented byanother means of regulation, which in this case functions by varying theflow cross section in accordance with the variations in the expulsionpressure under which the product flows out through the regulator.

The regulator shown in FIG. 10 closely resembles the one shown in FIGS.1 and 2, with the difference that the rigid disk 7 exhibits twelvegrooves 9 in the protrusion 8, instead of six, and that a regulatingdisk 18 is housed between the rigid disk 7 and the sealing disk 12,inside a chamber 30 which is not visible, but which is provided in thedownstream face of the rigid disk 7, just as illustrated in FIG. 4. Whenthis regulator comes into operation, because the valve of the aerosolcontainer has been opened, the flexible disk 6 is displaced towards theupstream face of the rigid disk 7, so that the grooves 9 become ducts,giving rise to turbulence effects at the mouth of the axial duct 10. Theproduct then displaces the regulating disk 18 onto the upstream surfaceof the sealing disk 12, thus covering the bore 13. The force exerted bythe leaf springs 21 and 22 is chosen to be such that a minimum flowcross-section persists between the downstream face of the regulatingdisk 18 and the upstream face of the sealing disk 12,; so as toguarantee a minimum flow rate when the product is being expelled under ahigh pressure. As the expulsion pressure falls, the leaf springs 21 and22 relax proportionately, and lift the regulating disk 18, this liftingmovement gradually increasing the flow cross-section in like proportionto the fall in the expulsion pressure.

FIG. 11 shows a further embodiment of a regulator, housed in acylindrical enclosure 51, exhibiting a supply duct 52, which opens intothe chambers 53 and 54. A regulating disk 55 is located inside thechamber 54, this disk 55 preferably being made of stainless steel andexhibiting a notch 56, located on its centerline and in the direction inwhich the metal was rolled. This regulating disk 55 is given acurvature, 57, which is preferably perpendicular to the notch 56 andhence perpendicular to the direction in which the metal was rolled. Thespring force resulting from the curvature 57 is very strong, givinglittle possibility of adjustment if the curvature is made in thedirection of rolling. On the other hand, a curvature, 57, madeperpendicularly to the direction of rolling offers a weaker springforce, with a wider range of adjustment. The spring force can also beadjusted with the aid of the notch 56: the greater its length, the moreit reduces the spring force. On the other hand, the length of the notch56 influences the product flow rate by extending more or less close to athrough-hole 59 in an accelerating disk 58. The notch 56 is essential byreason of the fact that a very high initial pressure inside the aerosolcontainer, for example 10 bars, could press the regulating disk 55 sohard against the accelerating disk 58 that the through hole could beclosed-off. This closing-off is prevented by the notch 56. A disk 62 islocated between the accelerating disk 58, with its through-hole 59, anda rigid disk 60, possessing a through-hole 61, the disk 62 exhibiting achamber 63. The size of the through-hole 59 brings about an accelerationof the product flow, while reducing the pressure under which it isexpelled, but which recovers in the chamber 63, so that the flow can beaccelerated anew by the reduced size of the through-hole 61, thepressure recovering, once again, in a chamber 64, belonging to anatomizing nozzle 65. The conversion, into expulsion pressure, of theproduct flow velocity, occurring in the chambers 63 and 64, is favorableto the quality of regulation achieved by the regulator. It must be notedthat the provision of a large through-hole 61 requires that, a higherspring force be exerted by the regulating disk 55, as opposed to whenthis hole 61 is small. Several parameters are therefore available forobtaining the required regulation. The thickness of the regulating disk55 is also one of these parameters. These different parameters enablethe regulator to be adjusted to suit the viscosities of the variousproducts which are to be dispensed, ranging from water, through alcoholand oil, to products of a creamy consistency.

The disk 62 is preferably manufactured as a plastic molding, while theaccelerating disk 58 and the rigid disk 60 are preferably made ofstainless steel. Due to this fact, the sizes of the through-holes 59 and61 cannot be affected by a solvent employed in an aggressiveformulation, for example methylene chloride. Moreover, the acceleratingdisk 58 and the rigid disk 60 cover the surface blemishes on theupstream and downstream faces of the disk 60, these blemishes derivingfrom the molding process, an example being the marks left by anextractor.

The regulating disk 55, the accelerating disk 58, the rigid disk 60, andthe disk 62 are held in place by the atomizing nozzle 65, which ispreferably like the one described in European Patent No. 688, and whichis firmly fixed inside the cylindrical enclosure 51, the dimensions ofthe said disks being chosen so as to ensure perfect sealing betweentheir peripheries and the said enclosure 51. This atomizing nozzle 65can be replaced by a simple tube, typically for dispensing oily orcreamy products.

The regulator shown in FIG. 11 operates in a manner which isillustrated, in part, by FIGS. 12 to 15, namely as follows: at rest,when the valve of the aerosol container is closed, the disk 55 is causedto bear, by its own spring force, against the through-hole 59 in theaccelerating disk 58, allowing the passages x (FIG. 14) to remaineffective. As soon as the pressure acting on the product to be dispensedacts on the regulating disk 55, the curvature 57 flattens out, thisflattening reducing the flow cross-section of the through-hole 59, sothat x becomes x-y (FIG. 15). As the expulsion pressure acting on theproduct to be dispensed falls, the spring force exerted by theregulating disk 55 re-establishes the shape of the curvature 57 in likeproportion, namely in proportion to the fall in the expulsion pressureprevailing in the product, and progressively opens the flowcross-section of the through-hole 59, so as to arrive, ultimately, atthe cross-section which provides the flow cross-section x, in particularwhen the aerosol container is becoming empty. The pressure prevailing inthe chamber 53 acts as a check on the inflow of product via thethrough-hole 59, namely as a retarding force which weakens progressivelyas the expulsion pressure falls, and which therefore forms one of themeans of regulation possessed by the regulator that has been described.

What is claimed is:
 1. A thrust regulator for dispensing a liquid at asubstantially constant flow rate from a container containing said liquidand a compressed gas, said thrust regulator comprisinga mountingenclosure having a first end and a second end, said first end having asupply duct formed therein, said supply duct connectable to a containercontaining a liquid and a compressed gas, said second end having anopening therein, said opening being receivable of a nozzle therein, saidmounting enclosure and said nozzle, when received in said opening,defining a chamber intermediate said nozzle and said supply duct; firstpressure-responsive flow control means, disposed in said chamber andfluidically connected to said supply duct, for inhibiting liquid flowthrough said supply duct in a manner substantially inverselyproportional to the pressure of said compressed gas in said container;flow retarding means, disposed in said chamber and fluidicallyconnecting said nozzle and said first pressure-responsive flow controlmeans, for retarding liquid flow from said first pressure-responsiveflow control means to said nozzle in a manner substantially inverselyproportional to the pressure of liquid exiting said firstpressure-responsive flow control means; said first pressure-responsiveflow control means and said flow retarding means cooperating to maintaina substantially constant liquid flow rate through said nozzlesubstantially independent of the pressure of said compressed gas.
 2. Thethrust regulator according to claim 1, wherein said flow retarding meanscomprises turbulence generating means for generating turbulent flow insaid liquid in substantially inverse proportion to the pressure ofliquid exiting said first pressure-responsive flow control means.
 3. Thethrust regulator according to claim 1, wherein said flow retarding meanscomprises second pressure-responsive flow control means for inhibitingliquid flow from said first pressure-responsive flow control means tosaid nozzle in a manner substantially inversely proportional to thepressure of liquid exiting said first pressure-responsive flow controlmeans.
 4. The thrust regulator according to claim 1, wherein said flowretarding means comprises:turbulence generating means, disposed in saidchamber and fluidically connected to said first pressure-responsive flowcontrol means, for generating turbulent flow in said liquid insubstantially inverse proportion to the pressure in liquid in saidsupply duct; and second pressure-responsive flow control means, disposedin said chamber and fluidically connecting said turbulence generatingmeans and said nozzle, for inhibiting liquid flow from said turbulencegenerating means to said nozzle in a manner substantially inverselyproportional to the pressure of liquid exiting said turbulencegenerating means.
 5. The thrust regulator according to claim 1, whereinsaid flow retarding means comprisesfirst accelerating means, fluidicallyconnected to said first pressure-responsive flow control means, forincreasing the linear velocity of said liquid to a velocity greater thanthat in said supply duct; pressurization means, fluidically connected tosaid first acceleration means, for decreasing the linear velocity ofsaid liquid exiting said first accelerating means; and secondacceleration means, fluidically connecting said pressurization means andsaid nozzle, for increasing the linear velocity of said liquid to avelocity greater than that in said pressurization means.
 6. The thrustregulator according to claim 2, wherein said turbulence generating meanscomprises a rigid disk having an upstream face and an axial passage,having a periphery, therethrough, said axial passage fluidicallyconnecting said nozzle and said first pressure-responsive flow controlmeans, said upstream face having at least two grooves formed thereinwhich form tangents to said periphery of said axial passage, said firstpressure-responsive flow control means and said rigid disk cooperatingto variably divert liquid flow from said first pressure-responsive flowcontrol means to said nozzle into said at least two grooves and thenceto said axial passage in substantially direct proportion to the pressureof liquid in said supply duct.
 7. The thrust regulator according toclaim 6, wherein said first pressure-responsive flow control meanscomprises a resilient disk abutting said upstream face of said rigiddisk, said resilient disk being continuously bendable in response toliquid pressure in said supply duct between a first position permittingliquid flow though said at least two grooves and a second positionsubstantially inhibiting liquid flow through said at least two grooves.8. The thrust regulator according to claim 7, wherein said resilientdisk has at least one notch therein.
 9. The thrust regulator accordingto claim 3, wherein said first pressure-responsive flow control meanscomprises: a rigid disk, having an axial passage therethrough, disposedwithin said chamber so that liquid flowing from said supply duct to saidnozzle must pass through said axial passage; a first flexible diskdisposed in said chamber intermediate said supply duct and said rigiddisk, said first flexible disk being continuously variably movable inresponse to liquid pressure in said supply duct between a first positioninhibiting liquid flow through said supply duct and a second positionpermitting liquid flow through said supply duct; first biasing means,disposed intermediate said first flexible disk and said rigid disk, foryieldably urging said first flexible disk to said first position and forinhibiting liquid flow through said axial passage in substantiallydirect proportion to the movement of said first flexible disk from saidfirst position to said second position; second flexible disk disposed insaid chamber intermediate said rigid disk and said nozzle, said secondflexible disk being continuously variably movable in response to liquidpressure in said axial passage between a first position inhibitingliquid flow through said axial passage and a second position permittingliquid flow through said axial passage; second biasing means, disposedintermediate said second flexible disk and said nozzle for yieldablyurging said second flexible disk to said first position and forinhibiting liquid flow through said nozzle in substantially directproportion to the movement of said second flexible disk from said firstposition to said second position.
 10. The thrust regulator according toclaim 9, wherein said first biasing means is incapable of completelyblocking flow through said axial passage and said second biasing meansis incapable of completely blocking flow through said nozzle.
 11. Thethrust regulator according to claim 4, wherein said turbulencegenerating means comprises a first rig disk having an upstream face anda first axial passage, having periphery, therethrough, said first axialpassage providing fluidic communication between said nozzle and saidfirst pressure-responsive flow control means, said upstream face havingat least two grooves formed therein which form tangents to saidperiphery of said first axial passage, said first pressure-responsiveflow control means and said rigid disk cooperating cause liquid flowfrom said first pressure-responsive flow control means to variably passthrough said at least two grooves and thence to said first axial passagein substantially direct proportion to the pressure of liquid in saidsupply duct;said first pressure-responsive flow control means comprisinga first resilient disk abutting said upstream face of said rigid disk,said first resilient disk being continuously bendable in response toliquid pressure in said supply duct between a first position permittingliquid flow through said at least two grooves and a second positionsubstantially inhibiting liquid flow through said at least two grooves;said second pressure-responsive flow control means comprising a secondrigid disk having an axial fluid passage therethrough, disposedintermediate said first rigid disk and said nozzle, and a secondflexible disk, disposed intermediate said first rigid disk and saidsecond rigid disk, said second flexible disk being continuously variablymovable in response to liquid pressure in said first axial passagebetween a first position permitting a predetermined maximum flow throughsaid second axial passage and a second position permitting apredetermined maximum flow through said second axial passage.
 12. Thethrust regulator according to claim 5, wherein said first acceleratingmeans comprises a first rigid disk, disposed intermediate said supplyduct and said nozzle, having a first axial fluid passagewaytherethrough, said first axial fluid passageway having a cross-sectionalarea less than the cross-sectional area of said supply duct;saidpressurization means comprises a second rigid disk, disposedintermediate said first rigid disk and said nozzle, having a secondaxial fluid passageway therethrough, said second axial, fluid passagewayhaving a cross-sectional area greater than the cross-sectional area ofsaid first axial fluid passageway; said second acceleration meanscomprises a third rigid disk, disposed intermediate said second rigiddisk and said nozzle, having a third axial fluid passagewaytherethrough, said third axial fluid passageway having a cross-sectionalarea less than the cross-sectional area of said second axial fluidpassageway.
 13. The thrust regulator according to claim 12, wherein saidfirst axial fluid passageway has a cross-sectional area less than thecross-sectional area of said third axial fluid passageway.